The condenser on a dry vacuum pump reduces emissions by trapping 90% of residual vapors. Image: Vacuubrand Inc.Discussions of lab vapor management in the context of sustainability tend to focus on energy conservation without compromising personnel safety. Fume hoods use a lot of energy to protect users from noxious vapors, so we look for safe ways to reduce that energy burden. What we don’t talk about is where all the exhausted vapors go, though we know they don’t just disappear.

Thoughtful observers of pollution-control strategies have long-since dismissed the notion that “the solution to pollution is dilution.” Yet, isn’t this what we are doing with our labs, relying on powerful roof fans to pump these noxious vapors into the air, to disperse them away from our work areas? Aren’t we just ignoring the fact they eventually fall back on our neighbors? We propose giving more attention to the emissions from lab facilities that strive for sustainability.

It’s easy to dismiss lab building emissions as small compared with industrial discharges, and so not worth attention. And it’s true waste vapor streams vary greatly in amount and character, making them difficult to characterize for control. It’s also true we dilute them with lots of fresh air, so the emitted concentrations are low. Yet, these observations simply evade the question, even as there are indications the problem may be bigger than we assume.

As an example, while the EPA defines “de minimis” releases as up to a ton per year of any one hazardous air pollutant, there are many different chemicals, and many labs. Published studies estimate that 10 to 30% of all solvents used in labs are lost as emissions, which isn’t surprising, since the goal of many lab processes is to evaporate solvents and exhaust them through fume hoods.

The problem is we don’t have good information about total volume of waste vapors emitted from labs, or even mass balance data on individual labs, much less the health effects of the persistent releases of small quantities of pollutants. These releases are the “second-hand smoke” of lab operations. The toxicity of the solvents used in labs gives us good reason to pump them out of our workspaces, but don’t we have a responsibility to evaluate the risks to our neighbors by doing so?

We contend the goal should be to collect as many of these waste vapors and prevent their release. Let’s briefly touch on two technologies that can help. Filtered fume hoods are one such technology; condensers on vacuum pumps are another.

Filtered fume hoods don’t have exhaust ducts. Instead, they use carbon-based chemical filtration to trap chemicals used in the hood (and the lab). In many cases, there’s no incremental investment in filtered hoods compared with standard ducted hoods, despite the higher unit costs; reduced volumes of exhausted air yield savings on HVAC infrastructure. As for operating costs, building energy savings offset the costs of periodic filter replacement. Meanwhile, replaced filters and their contaminants are destroyed by high-temperature incineration with 99.99% efficiency. Filtered fume hoods aren’t an appropriate replacement for ducted hoods in all circumstances, but used where appropriate they can dramatically reduce total building emissions at no incremental cost.

A second way to reduce releases of waste solvent vapors is to equip vacuum pumps with condensers. Many lab operations are vacuum-driven evaporative processes: drying, concentration, distillation. Even a well-managed rotary evaporator, however, will capture only about 85 to 90% of the vapors passing through its condenser; 10 to 15% of waste vapors are exhausted through fume hoods and roof fans. Alternatively, an oil-free pump equipped with an exhaust condenser can capture 90% of the residual vapors. In combination with the rotary evaporator’s condenser, that amounts to 98% solvent recovery. Use a similarly equipped pump on a local vacuum network supporting multiple vacuum workstations, and you can collect most of the vacuum process vapors in the lab, before they are exhausted.

Neither technology cited gets us to 100% recovery, but we can remove a large fraction of solvent vapors before sending them out the top of lab buildings. We contend a sustainable lab building can’t ignore its “second-hand smoke” problem.

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Peter Coffey joined VACUUBRAND in 2009 with the mission of bringing to North America energy- and water-saving lab vacuum technology developed by VACUUBRAND of Germany. Earlier, Coffey served as VP of Marketing for BrandTech Scientific Inc. and has held various sales and marketing positions in companies supplying to the scientific markets.

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